Learn About

THE MOON

The Moon is an astronomical body that orbits planet Earth, and is Earth's only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits (its primary). The Moon is after Jupiter's satellite Io the second-densest satellite in the Solar System among those whose densities are known.

The Moon is thought to have formed about 4.51 billion years ago, not long after Earth. The most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a Mars-sized body called Theia.

The Moon is in synchronous rotation with Earth, and thus shows always the same side to earth, the near side. The near side is marked by dark volcanic maria that fill the spaces between the bright ancient crustal highlands and the prominent impact craters. The moon is after the sun the second-brightest regularly visible celestial object in Earth's sky. Its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its gravitational influence produces the ocean tides, body tides, and the slight lengthening of the day.

The Moon's average orbital distance is 384,402 km (238,856 mi),or 1.28 light-seconds. This is about thirty times the diameter of Earth. The Moon's apparent size in the sky is almost the same as that of the Sun (because it is 400x farther and larger). Therefore, the Moon covers the Sun nearly precisely during a total solar eclipse. This matching of apparent visual size will not continue in the far future, because the Moon's distance from Earth is slowly increasing.

+ CRATERS ON THE MOON

The other major geologic process that has affected the Moon's surface is impact cratering, with craters formed when asteroids and comets collide with the lunar surface. There are estimated to be roughly 300,000 craters wider than 1 km (0.6 mi) on the Moon's near side alone. The lunar geologic timescale is based on the most prominent impact events, including Nectaris, Imbrium, and Orientale, structures characterized by multiple rings of uplifted material, between hundreds and thousands of kilometres in diameter and associated with a broad apron of ejecta deposits that form a regional stratigraphic horizon.

+ WHAT IS THE LARGEST CRATER ON THE MOON?

South Pole-Aitken Basin. Found on the far side of the Moon, the diameter of this impact crater is equivalent to the distance from London to Athens. The massive Aitken basin measures 2,500 kilometres (1,600 miles) across and is the largest, deepest and oldest basin on the Moon.

+ MAIN FEATURES ON THE MOON

While the craters, highlands and Maria are the moon's three main landforms, the moon's surface has a number of other highly visible features. For example, some impact craters have bright rays that shoot outward from the centre. Also, the moon has a number of rilles, which are long, thin tunnels or trenches.

+ WHY THE MOON IS SO IMPORTANT TO EARTH

Perhaps the most important effect of the Moon is the way it stabilizes our rotation. When the Earth rotates it wobbles slightly back and forth on its axis. It's like a top, which doesn't simply spin in a vertical position on a table or the floor. But without the Moon we'd be wobbling much more

+ WHAT WOULD HAPPEN IF EARTH HAD NO MOON

One of the Moon's most noticeable effects is (or was) the tides. With theMoon no longer there, the oceans of the world become much calmer. The Sun still has an effect on them (known as solar tides), so surfers wouldn't be completely devoid of waves. But the oceans would largely become serene

+ CAN A COUNTRY CLAIM THE MOON

According to the United Nations Outer Space Treaty, signed by every space-faring country, no nation can claim sovereignty over Earth's lunar satellite. 102 countries have entered into to the 1967 accord; China joined in 1983.

+ FIRST PERSON ON THE MOON

The first person to set foot on the Moon was Neil Armstrong

+ IS THERE WATER ON THE MOON?

Although research is continuing, most scientists agree that the Moon features small amounts of water.

+ WHAT OR THE MOON PHASES?

The phases of the Moon are: New Moon, Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, Crescent & New Moon.

+ WHAT IS THE HEIGHTS MOUNTAIN ON THE MOON?

Mons Huygens is the tallest mountain on the Moon, it is 4700 metres tall, just over half the height of Mt Everest (8848m).

+ HOW OFTEN DOES THE MOON ORBIT EARTH?

The Moon orbits the Earth every 27.3 days.

+ IS THERE GRAVITY ON THE MOON?

The effect of gravity is only about one fifth (17%) as strong on the surface of the Moon compared to the strength of gravity on the surface of the Earth.

+ HOW LONG DOES IT TAKE TO TRAVEL TO THE MOON FROM EARTH?

It takes about 3 days for a spacecraft to reach the Moon. During that time a spacecraft travels at least 240,000 miles (386,400 kilometers) which is the distance between Earth and the Moon. The specific distance depends on the specific path chosen.